Semiconductor laser beam device

ABSTRACT

A semiconductor laser beam device, comprising a stem type package having a base part and a heat sink part, wherein the heat sink part is cylindrically formed so as to be concentric to the base part, a groove is formed along the axial direction of the heat sink part, and a semiconductor laser beam element is disposed at the bottom part of the inner wall surfaces of the groove whereby the radiating capability of the semiconductor laser beam device can be increased by increasing the volume of the heat sink part, and the element can be protected by the groove.

TECHNICAL FIELD

The present invention relates to a semiconductor laser device for use asa light source for an optical disk such as a CD, CD-R/RW, DVD, DVD-R/RW,DVD-Blu-Ray disk, and the like. More particularly, the present inventionrelates to a semiconductor laser device having a compact packagesuitable for use as a slim (thin) pickup for an optical disk, and to apackage therefor.

BACKGROUND ART

Currently used half-height pickups employ semiconductor laser deviceswith a 5.6-mm-diameter stem. For slim pickups, packages with a D-shapedstem, obtained by cutting off a portion of a 5.6-mm-diameter stem, anI-shaped stem, obtained by cutting off opposite portions of a5.6-mm-diameter stem, or the like have been proposed. Also proposed arepackages with a 3.5- or 3.3-mm-diameter stem (see an exterior view shownin FIG. 13). However, packages with these 3.5- and 3.3-mm-diameter stemsare, as will be understood from the external view thereof shown in FIG.13, simply down-scaled versions of a package with a 5.6-mm-diameterstem, and thus have, inconveniently, accordingly smaller heat sinks onwhich to place laser devices. Constructions with increased heat sinkvolumes are also known, for example in Patent Publication 1. However,even these constructions, with semicircular heat sinks, do not offersufficient volumes.

High-output semiconductor laser devices for CD-Rs and DVD-Rs requirelarger currents and higher voltages, and thus generate accordinglylarger amounts of heat. This makes it difficult to guarantee normaloperation at high temperatures of 70° and above by the use of a stemwith a small heat-dissipation volume such as a 3.3-mm-diameter stem.Thus, it is important to devise how to maximize the heat-dissipationvolume.

DISCLOSURE OF THE INVENTION

The present invention aims to achieve at least one, and hopefully more,of the following objects: to achieve improved heat dissipation; toobtain compact packages; to protect elements, and to reduce the numberof lead pins.

To achieve the above objects, according to the present invention, asemiconductor laser device is characterized in that a groove is formedin a cylindrical heat sink along the axial direction thereof and in thata semiconductor laser element is placed on an inner wall surface of thegroove.

This helps increase the heat sink volume and thereby enhance the heatdissipation of the semiconductor laser device.

According to the present invention, a semiconductor laser device havinga package comprising a circular base and a heat sink and having asemiconductor laser element placed on the heat sink is characterized inthat the heat sink is cylindrical and concentric with the base, in thata groove is formed in the heat sink along the axial direction thereof,and in that the semiconductor laser element is placed on an inner wallsurface of the groove.

With this construction, the omission of the conventionally used airtightstructure helps reduce the number of components and the number ofassembly steps. Moreover, it is possible to increases the area overwhich the heat sink makes contact with outside air.

According to the present invention, the groove is formed so deep as toinclude the center axis of the cylindrical heat sink.

This makes it possible to place the semiconductor laser element with theoptical axis thereof aligned with the center axis of the cylindricalheat sink. Thus, it is possible to prevent misalignment of the opticalaxis resulting from rotation during assembly into a pickup apparatus orthe like.

According to the present invention, the groove is so shaped as tocompletely house therein the semiconductor laser element.

When the semiconductor laser element is housed in a groove whose depthis much greater than its own height in this way, the walls serve toprotect the element.

According to the present invention, the groove is so shaped as tocompletely house therein the semiconductor laser element along withbonding wires connected thereto.

This permits the semiconductor laser element and the bonding wires to beprotected by the side walls.

According to the present invention, the walls located at both sides ofthe groove extend to a height higher than the semiconductor laserelement.

When the semiconductor laser element is placed so as to be locatedbetween walls whose height is much greater than its own height in thisway, the walls serve to protect the element.

According to the present invention, the groove is formed by cutting offan arc surface of the heat sink equivalent to a center angle of 180degrees or less.

With this construction, the surface located at the bottom of the grooveis a flat surface parallel to the center axis of the cylinder, and thesemiconductor laser element is placed on this flat surface.

According to the present invention, a lead pin is provided that, at oneend thereof, penetrates the base, and the lead pin is, at the other endthereof, located in the groove.

With this construction, a wire can be bonded inside the groove. Thismakes it possible to securely protect the wire with the heat sink.

According to the present invention, two lead pins are provided that, atone ends thereof, penetrate the base, and the lead pins are, at one endsthereof, located in the groove.

With this construction, even with a semiconductor laser device thatincorporates a light-receiving element, a lead pin that penetrates thebase can be, at one end, placed inside the groove, and thus a wire canbe bonded inside the groove. This makes it possible to securely protectthe wiring for the light-receiving element with the heat sink. Moreover,it is also possible to make the package compact.

According to the present invention, the heat sink has a tapered surfaceformed along the outer edge of the tip end thereof.

Forming the taper surface in this way prevents an edge from shaving theportion, typically formed of aluminum or the like, of an optical pickupwhere it receives the laser device.

According to the present invention, the heat sink has the tip endthereof formed into a spherical surface.

This permits the tip end of the semiconductor laser device to be shapedlike the tip of a ballpoint pen, and thus makes it easy to pan and tiltthe device for adjustment during assembly into a pickup apparatus or thelike. Specifically, it is easy to perform so-called pan-and-tiltadjustment whereby, with the tip end of the laser device placed in asemispherical dent formed in the pickup apparatus, the lead-pin-sideportion of the device is so moved as to bring the optical axis into anoptimally aligned position.

According to the present invention, the heat sink has the bottom surfacethereof formed flat.

By making the bottom surface flat in this way, it is possible to stablyhold the package when wires are bonded to the semiconductor laserelement and other components.

According to the present invention, a flat-plate-shaped optical elementis attached to the front end surface of the heat sink.

By incorporating into the semiconductor laser device an optical element,which is conventionally provided separately therefrom, in this way, itis possible to simplify the optical alignment required in an opticalpickup or in an optical communication transmitter.

According to the present invention, a spherical optical element isattached to the front end surface of the heat sink.

By incorporating into the semiconductor laser device an optical element,which is conventionally provided separately therefrom, with opticalalignment performed beforehand in this way, it is possible to simplifythe optical alignment required when the device is applied to an opticalpickup, an optical communication transmitter, or an optical fibermodule.

According to the present invention, the base and the heat sink areformed of the same metal.

This permits the base and the heat sink to be formed integrally. Forexample, these can be formed simultaneously by pressing a sheet-shapedmaterial, or by cutting a column-shaped material.

According to the present invention, a semiconductor laser device ischaracterized in that a groove so deep as to completely house therein asemiconductor laser element is formed in a columnar heat sink, and inthat the semiconductor laser element is placed on the bottom of thegroove.

With this construction, it is possible to protect the element with thegroove.

According to the present invention, a semiconductor laser devicecomprising a semiconductor laser element and a columnar heat sink havinga flat surface that is parallel to the optical axis of the semiconductorlaser element and on which the semiconductor laser element is placed ischaracterized in that the heat sink has a wall formed integrallytherewith at one of the left-hand and right-hand sides of the flatsurface with respect to the optical axis, and in that the summit of thewall is located higher than the semiconductor laser element and than thebonding wire connected thereto.

In this way, the presence of the wall helps increase theheat-dissipation volume or surface area and thereby achieve satisfactoryheat dissipation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a first embodiment of the invention, in a perspective view(a), a front view (b), and a plan view (c).

FIG. 2 shows a second embodiment of the invention, in a perspective view(a), a front view (b), and a plan view (c).

FIG. 3 shows a third embodiment of the invention, in a perspective view(a), a front view (b), and a plan view (c).

FIG. 4 shows a fourth embodiment of the invention, in a partly cut-outside view (a) and a front view (b).

FIG. 5 shows a fifth embodiment of the invention, in a plan view (a) anda front view (b).

FIG. 6 shows a sixth embodiment of the invention, in a plan view.

FIG. 7 shows a seventh embodiment of the invention, in a front view.

FIG. 8 shows an eighth embodiment of the invention, in a perspectiveview.

FIG. 9 shows a ninth embodiment of the invention, in a perspective view(a), a front view (b), and a plan view (c).

FIG. 10 shows a tenth embodiment of the invention, in a perspective view(a), a front view (b), and a plan view (c).

FIG. 11 shows an eleventh embodiment of the invention, in a perspectiveview (a), a front view (b), and a plan view (c).

FIG. 12 is a characteristics diagram showing the data obtained inreliability tests.

FIG. 13 shows a conventional example, in a partly cut-out perspectiveview.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

FIG. 1 shows the semiconductor laser device of a first embodiment of theinvention, in a perspective view (a), a front view (b), and a plan view(c).

The semiconductor laser device 1 has a stemmed package 2. This package 2consists essentially of a base 3 and a heat sink 4.

The base 3 basically has the shape of a disk with a diameter of 3.3 mmand a thickness of 1 mm, and is built as a disk-shaped metal member. Theheat sink 4 basically has the shape of a cylinder with a diameter of 2.9mm and a length of 2.5 mm, and is built as a column-shaped metal memberof which a portion is cut out to form a depression. The base 3 and theheat sink 4 are arranged concentrically so that, as seen from the front,their centers coincide. The center X of the base 3 and the heat sink 4is so located as to coincide with the optical axis X of thesemiconductor element described later.

The heat sink 4 has a groove 5 formed therein. The groove 5 extendsalong the center axis of the cylinder, and cuts the upper and lower flatsurfaces of the cylinder. Thus, the heat sink 4 is U-shaped as seen fromthe front. The groove 5 is so formed as to be increasingly wide frombottom to top, specifically 1.5 mm wide at the top end and 1.0 mm wideat the bottom end. The groove 5 is so formed that the arc portion of thecylinder cut off as the groove 5 (i.e., the arc portion of the cylinderof which the chord is described by the top end of the groove 5) covers,when converted to a center angle about the center axis of the cylinder,an angle θ smaller than 180 degrees. This angle θ is set to be smallerthan 90 degrees, but may be set to be larger than 90 degrees so long asit is smaller than 180 degrees. The groove 5 is so formed that thebottom surface thereof is located deeper than the center axis X of thecylinder. The surface 6 located at the bottom of the groove 5 is formedinto a flat surface parallel to the center axis X of the cylinder. Thissurface 6 is used as the surface on which the semiconductor elementdescribed later is placed.

The heat sink 4 has walls 7 formed integrally therewith at both sides(on the left-hand and right-hand sides with respect to theabove-mentioned axis X) of the flat surface 6. That is, it has, on theleft-hand and right-hand sides of the groove 5, left-hand and right-handwalls 7A and 7B that are higher than the flat surface 6 at the bottom ofthe groove 5. Between these walls 7A and 7B, the element 9 describedlater is placed.

The heat sink 4 has the base end thereof formed integrally with the base3. One way to form the package 2 is to form the base 3 and the heat sink4 as separate members and then join them together into a single memberwith a connecting material such as solder. Another way to form thepackage 2 is to form the base 3 and the heat sink 4 integrally as asingle member. When the base 3 and the heat sink 4 are formed asseparate members, it is preferable that the base 3 be formed of copperor copper-based alloy, which has low thermal resistance, or iron oriron-based alloy, and that the heat sink 4 be formed of copper orcopper-based alloy, which has low thermal resistance. When the base 3and the heat sink 4 are formed integrally, it is preferably that they beformed of copper or copper-based alloy, which has low thermalresistance. When the base 3 and the heat sink 4 are formed integrally,they can be formed simultaneously by pressing a sheet-shaped material,or by cutting a column-shaped material.

The heat sink 4 has a tapered surface 8 formed around the edge of thetip end thereof so that the heat sink 4 tapers off at the tip endthereof. Forming this taper surface 8 helps prevent an edge from shavingthe portion, typically formed of aluminum or the like, of an opticalpickup where it receives the laser device.

Moreover, the heat sink 4 has the outer circumferential surface thereofformed as a curved surface describing an arc about the axis X andincluding left-hand and right-hand walls 7A and 7B. Thus, when theposition of the laser device in the portion of an optical pickup whereit receives the laser device is adjusted by rotating the laser device,the outer circumferential curved surface thereof serves as a guide,permitting smooth movement of the laser device during adjustment.

The semiconductor laser device 1 has a semiconductor laser element 9, asa semiconductor element, placed on the package 2. The semiconductorlaser element 9 is placed on a fitting surface of the heat sink 4,specifically, in this example, on a flat surface 6 that is part of theinner wall surface of the groove 5, with a submount 10 interposed inbetween. For enhanced heat dissipation, it is preferable that thesemiconductor laser element 9 be placed in a junction-down arrangement,i.e., with the light-emitting point thereof lopsided toward the submount10.

In the semiconductor laser device 1, it is possible to use asemiconductor laser element 9 of any type, ranging from infrared toultraviolet regions. Among these, it is preferable to use asemiconductor laser element of a red- or blue-region type that exhibitspoorer heat dissipation than a semiconductor laser element of aninfrared-region type and that thus requires a better heat dissipationenvironment, because this helps improve the heat dissipation of such asemiconductor laser element.

The submount 10 is formed as a member that dissipates heat well, and isformed of, for example, a semiconductor material such as silicon oraluminum nitride. To further enhance the heat dissipation of thesemiconductor laser element 9, the semiconductor laser element 9 may befitted directly to the fitting surface of the heat sink 4 without thesubmount 10 interposed in between.

The semiconductor laser element 9 is placed inside the groove 5, and isthus arranged sandwiched between the walls 7A and 7B, of which theheight is much greater than the height of the semiconductor laserelement 9 itself. Thus, these walls serve to protect the element.

The semiconductor laser device 1 is provided with a plurality of leadpins 11A and 11B that are fixed to the package 2. In this embodiment,two lead pines 11A and 11B are so arranged as to sandwich the center Xof the base 3. One lead pin 11A is jointed, by welding or the like, tothe base 3, and is thereby fixed to the base 3 in a state electricallyconductive therewith. The other lead pin 11B is, at one end, put througha through hole 12 formed in the base 3, and is fixed to the base 3 in astate electrically insulated from the base 3 by an insulating member 13placed inside the through hole 12. This lead pin 11B, at one end,penetrates the base 3 and is located inside the groove 5.

The one lead pin 11A is connected, via the base 3, the heat sink 4, abonding wire 14, and the like, to one electrode of the semiconductorlaser element 9. The other lead pin 11B is connected, via a bonding wire15 connected to one end thereof, a conductor laid on the submount 10,and the like, to the other electrode of the semiconductor laser element9. When a voltage needed to drive the semiconductor laser element 9 isapplied between the lead pins 11A and 11B, the semiconductor laserelement 9 operates, and emits laser light in the direction of the axisX.

For the bonding wires 14 and 15 to be protected by the side walls 7A and7B, it is preferable that the bonding wires 14 and 15 be arranged insidethe groove 5 so as not to protrude from the upper edge of the groove 5.That is, the groove 5 is so shaped as to completely house therein thesemiconductor laser element 9, the submount 10, and the bonding wires 14and 15.

In the base 3 of the semiconductor laser device 1 are formed, asconventionally practiced, a pair of triangular cuts 16A and 16B forpositioning and a rectangular cut 17 for orientation indication.

The semiconductor laser device 1 as a finished product is shown in FIG.1, and is incorporated into an optical pickup apparatus or the like soas to be used as a light source therefor. At this time, since the heatsink 4 has the tapered surface 8 at the tip end thereof, it is possibleto insert the semiconductor laser device 1 into the position where it isto be mounted. Moreover, the tapered surface 8 formed at the tip end ofthe semiconductor laser device 1 prevents an edge from shaving theportion, typically formed of aluminum or the like, of an optical pickupwhere it receives the laser device. In this way, it is possible toprevent the optical system from being adversely affected by metalparticles produced as a result of shaving by an edge. When thesemiconductor laser device is incorporated in an optical pickupapparatus or the like for actual use, the heat sink 4 side flat surfaceof the base 3 functions as a reference surface for positioning.

In the embodiment shown in FIG. 1, the heat sink 4 has a volume of 11.1mm³, which is about ten times the comparable volume, specifically 1.1mm³, in the conventional type (with a diameter of 3.5 mm) shown in FIG.10. The overall volume of the package 2 (the total volume of the base 3and the heat sink 4) is 20.7 mm³, which is about twice the comparablevolume, specifically 10.7 mm³, in the conventional type shown in FIG.13. The proportion of the volume of the heat sink 4 in the overallvolume of the package 2 is about 53% (11.1/20.7), which is about fivetimes the comparable proportion, specifically about 10% (1.1/10.7), inthe conventional type shown in FIG. 13. Thus, it is possible toeffectively dissipate the heat generated by the semiconductor laserelement 9.

FIG. 12 shows the results of reliability tests in which a semiconductorlaser device having a red-region semiconductor laser element anddesigned for a DVD-R was fed with 100 mW pulses in a 70° C. environment.Along the horizontal axis is taken the lapse of time, and along thevertical axis is taken the operation current under APC (automatic powercontrol). As will be clear from this graph, it was confirmed that,whereas the conventional construction shown in FIG. 13 made the deviceinoperable in about 100 hours, the construction of this embodimentpermitted the device to operate stably for 500 hours and more.

In this embodiment, the conventional airtight structure employing a capis not adopted. This helps reduce the number of components and thenumber of assembly steps. Moreover, it is also possible to increase thearea over which the heat sink 4 makes contact with outside air.

It is also possible to build a semiconductor laser device byadditionally fitting a cap having a window, as conventionally used,airtightly on the construction shown in FIG. 1.

The semiconductor laser device 1 shown in FIG. 1 does not incorporate alight-receiving element. Accordingly, to monitor the output of thesemiconductor laser element 9, it is preferable to arrange, separatelyfrom the semiconductor laser device 1, a light-receiving element forfront monitoring.

Next, a second embodiment of the invention will be described withreference to FIG. 2. Such components as are found also in the embodimentshown in FIG. 1 are identified with the same reference numerals, andtheir explanations will be omitted; that is, the following descriptioncenters on differences from the first embodiment. The main differencesfrom the first embodiment are the use of a submount 10 incorporating alight-receiving element 18 and the use of one more lead pin for theextraction of the output thereof, making the total number of lead pinsthree.

In the base 3, there is formed one laterally elongate through hole 12that is large enough to put two lead pins 11B and 11C therethrough.Through this hole 12 are arranged the two lead pins 11B and 11C apartfrom each other and in such a way that they are, at one ends, locatedinside the groove 5. These two lead pins 11B and 11C are fixed to thebase 3 in a state insulated from each other and from the base 3 by aninsulating member 13. As in the previous embodiment, one end of the leadpin 11B is used for the wiring of the semiconductor laser element 9, andthe other lead pin 11C is used for the wiring of the light-receivingelement 18 incorporated in the submount 10. The light-receiving element18 is a PIN-type light-receiving element having a two-terminalstructure, with the electrode (in this example, the rear-side electrode)connected to one terminal thereof electrically connected to the heatsink 4, and the other electrode (in this example, the obverse electrode)connected via a bonding wire 19 to the lead pin 11C.

The second embodiment offers the same effects as the first embodiment.In addition, even in the case of a semiconductor laser deviceincorporating a light-receiving element, the lead pins 11B and 11C thatpenetrate the base 3 can be, at one ends, located inside the groove 5 sothat bonding wires can be laid inside the groove 5. Thus, it is possibleto securely protect the wiring for the light-receiving element 18 withthe heat sink 4. It is also possible to make the package 2 compact.

Next, a third embodiment of the invention will be described withreference to FIG. 3. Such components as are found also in the embodimentshown in FIG. 1 are identified with the same reference numerals, andtheir explanations will be omitted; that is, the following descriptioncenters on differences from the first embodiment. The main differencefrom the first embodiment is that the heat sink 4 has, at the tip endthereof, a semispherical curved surface 20 instead of the taperedsurface 8. The semiconductor laser element 9 and the submount 10 are soarranged as not to protrude from this curved surface 20. Forming thiscurved surface 20 permits the tip end of the semiconductor laser device1 to be shaped like the tip of a ballpoint pen, and thus makes it easyto pan and tilt the device for adjustment during assembly into a pickupapparatus or the like. Specifically, it is easy to perform so-calledpan-and-tilt adjustment whereby, with the tip end of the laser deviceplaced in a semispherical dent formed in the pickup apparatus, thelead-pin-side portion of the device is so moved as to bring the opticalaxis into an optimally aligned position.

In the third embodiment, the semiconductor laser element 9 can be movedslightly frontward or rearward along the direction of the axis X (forexample toward the base 3) from the position shown in FIG. 3. Forexample, it is possible to place the semiconductor laser element 9 insuch a way that the light emission point thereof is equidistant from thecurved surface 20. That is, when the curved surface 20 is regarded aspart of a sphere, the semiconductor laser element 9 can be placed insuch a way that the light emission point thereof is located at thecenter of the sphere. With this arrangement, the light emission point ofthe semiconductor laser element 9 does not move during the pan-and-tiltadjustment mentioned above. This makes adjustment easy.

The third embodiment can be applied to the second embodiment and toother embodiments described later.

Next, a fourth embodiment of the invention will be described withreference to FIG. 4. Such components as are found also in the embodimentshown in FIG. 1 are identified with the same reference numerals, andtheir explanations will be omitted; that is, the following descriptioncenters on differences from the first embodiment. The main differencefrom the first embodiment is that the shape of the heat sink 4 ismodified. A first modified point lies in a downward sloped taperedsurface 21 being formed at the tip end of the flat surface 6 of thegroove 5. Forming this tapered surface 21 helps prevent the lightoutputted from the semiconductor laser element 9 from being interceptedby the flat surface 6 of the groove 5. The slope angle of the taperedsurface 21 is set to be larger than the angle at which the light fromthe semiconductor laser element 9 diverges in the up and downdirections. The angle at which the light from the semiconductor laserelement 9 diverges in the up and down directions typically is about 30degrees, and therefore the slope angle of the tapered surface 21 can beset to be 15 degrees or more, for example an angle in the range from 15degrees to 20 degrees.

For example, in a case where the heat sink 4 is made longer while theposition of the semiconductor laser element 9 is kept unchanged, formingthe tapered surface 21 makes it easy to make the heat sink 4 longer.This makes it possible to increase the volume of the heat sink 4, and toincrease the heat dissipation area.

A second modified point lies in the bottom surface of the groove 5 beingformed into a flat bottom surface 22 instead of the arc-shaped surface.This bottom surface 22 is a flat surface parallel to the surface 6 ofthe groove 5, and has a larger area than the surface 6. Forming thisflat bottom surface 22 makes it possible to stably hold the package 2when wire bonding is performed on the semiconductor laser element 9 andother components.

The first and second modified points described above may be carried outseparately or simultaneously.

The fourth embodiment can be applied to the second and third embodimentsand to other embodiments described later.

Next, a fifth embodiment of the invention will be described withreference to FIG. 5. Such components as are found also in the embodimentshown in FIG. 1 are identified with the same reference numerals, andtheir explanations will be omitted; that is, the following descriptioncenters on differences from the first embodiment. The main differencesfrom the first embodiment are that the shape of the heat sink 4 ismodified, and that an optical element 23 is added to the tip endthereof.

A first modified point lies in the tip end of the heat sink 4 being leftcylindrical without forming the tapered surface 8 there. That is, thetip-end and base-end surfaces of the heat sink 4 have the same shape asseen in a plan view. By giving the tip end of the heat sink 4 such ashape, it is possible to secure a large area on the tip-end surface 24of the heat sink 4. Thus, it is possible to secure a wide margin forfitting the optical element 23 to the tip-end surface 24 of the heatsink 4.

A second modified point lies in the addition of the optical element 23to the tip end of the heat sink 4. This optical element 23 is shapedlike a flat plate, but may be shaped otherwise so long as it is flat onthe surface thereof facing the heat sink 4. For example, a taperedsurface like the tapered surface 8 may be formed on the surface of theoptical element 23 facing away from the heat sink 4. Used as the opticalelement 23 is one selected from among a hologram element, a quarter-waveplate, a polarizer plate, a plate-shaped lens, and the like. Byincorporating into the semiconductor laser device the optical element23, which is conventionally provided separately therefrom, it ispossible to simplify the optical alignment required in an optical pickupor in an optical communication transmitter.

The first and second modified points described above may be carried outseparately or simultaneously.

The fifth embodiment can be applied to the second and fourth embodimentsand to other embodiments described later.

Next, a sixth embodiment of the invention will be described withreference to FIG. 6. Such components as are found also in the embodimentshown in FIG. 2 are identified with the same reference numerals, andtheir explanations will be omitted; that is, the following descriptioncenters on differences from the second embodiment. The main differencesfrom the second embodiment are that the shape of the heat sink 4 ismodified, and that an optical element 25 is added to the tip endthereof.

The first modified point lies in the tip end of the heat sink 4 beingleft cylindrical without forming the tapered surface 8 on the outsidethereof. Instead, at the tip end of the groove 5, there is formed a dentfor receiving the optical element 25. Giving the tip end of the heatsink 4 such a shape makes it possible to securely fit the sphericaloptical element 25.

The second modified point lies in the spherical optical element 25 beingadded to the tip end of the heat sink 4. This optical element 25 is usedto collimate or condense the light emitted from the semiconductor laserelement 9. The optical element 25 is held in the dent formed at the tipend of the heat sink 4, and is fixed thereto with adhesive or the like.By incorporating into the semiconductor laser device the optical element25, which is conventionally provided separately therefrom, with opticalalignment performed beforehand, it is possible to simplify the opticalalignment required when the device is applied to an optical pickup, anoptical communication transmitter, or an optical fiber module.

The first and second modified points described above may be carried outseparately or simultaneously.

The sixth embodiment can be applied to the first, fourth, and otherembodiments.

Next, a seventh embodiment of the invention will be described withreference to FIG. 7. Such components as are found also in the embodimentshown in FIG. 1 are identified with the same reference numerals, andtheir explanations will be omitted; that is, the following descriptioncenters on differences from the first embodiment. The main differencefrom the first embodiment is that the shape of the arc-shaped sidesurface of the heat sink 4 is modified to a polyhedral shape. The outercircumferential surface of the heat sink 4, which has an arc-shapedportion as seen from the front in the first embodiment, is so modifiedas to have a polyhedral shape as seen from the front. Modifying thisportion to a polyhedral shape makes catching easy. The bottom surface ofthe heat sink 4, which is an arc-shaped surface in the first embodiment,is here a flat bottom surface 22 as in the fourth embodiment. Thisbottom surface 22 is a flat surface parallel to the surface 6 of thegroove 5, and has a larger area than the surface 6. Forming this flatbottom surface 22 makes it possible to stably hold the package 2 whenwire bonding is performed on the semiconductor laser element 9 and othercomponents.

To permit the heat sink 4 to be stably fitted when inserted into acylindrical dent, the heat sink 4 is so formed that a plurality ofcorners on the circumferential surface thereof are inscribed in animaginary cylinder (indicated by a dash-and-dot line C in FIG. 7). Here,the center axis of the imaginary cylinder coincides with the axis Xmentioned earlier.

The seventh embodiment can be applied to the second and otherembodiments.

Next, an eighth embodiment of the invention will be described withreference to FIG. 8. Such components as are found also in the embodimentshown in FIG. 1 are identified with the same reference numerals, andtheir explanations will be omitted; that is, the following descriptioncenters on differences from the first embodiment. The main differencefrom the first embodiment is that the shapes of the base 3 and of theheat sink 4 are modified.

A first modified point lies in the base 3 and the heat sink 4 beinggiven different exterior dimensions. Specifically, the flange surfaceused as a reference surface for positioning, i.e., the outercircumferential portion of the base 3 that protrudes from thecircumference of the heat sink 4, is eliminated. By giving the base 3and the heat sink 4 such an integral cylindrical shape and therebyeliminating the level difference between them, it is possible toeliminate the restrictions imposed by such a level difference when thefitting position of the semiconductor laser device is adjusted by movingit along the direction of the axis X. This makes adjustment easy.

A second modified point lies in, for higher wire bonding workability,part of the wall 7B of the heat sink 4 being removed, with a flatsurface 6B formed instead. The flat surface 6B is flush with the surface6 of the groove 5, but may be given a height difference relative to thesurface 6 of the groove 5. Forming this flat surface 6B helps reduce therestrictions on the shape of the capillary tool used to bond wires tothe semiconductor laser element 9 and the submount 10. This helpsenhance workability in the fabrication process.

The first and second modified points described above may be carried outseparately or simultaneously.

The eighth embodiment can be applied to any of the second to seventhembodiments and to other embodiments.

Next, a ninth embodiment of the invention will be described withreference to FIG. 9. Such components as are found also in the embodimentshown in FIG. 1 are identified with the same reference numerals, andtheir explanations will be omitted; that is, the following descriptioncenters on differences from the first embodiment. The main differencesfrom the first embodiment are that a dummy lead pin ID is provided tomake the semiconductor laser device compatible with common three-pindevices, and that one of the left-hand and right-hand walls 7A and 7Bformed at both left-hand and right-hand sides of the groove 5 is removedso that a wall 7B is formed at only one of the left-hand and right-handsides of the flat surface 6.

With one of the walls 7A and 7B removed, the heat sink 4 is L-shaped asseen from the front. In the previous embodiment, the semiconductor laserelement 9 is placed on the flat surface 6 that forms the bottom surfaceof the groove 5. By contrast, in a case where, as in this embodiment,the groove 5 can be regarded as fan-shaped (V-shaped), it is possible toregard the semiconductor laser element 9 as being placed on one of theinner wall surfaces of the groove 5.

The lead pin 11B is not completely housed inside the groove 5, but isfixed to the base 3 in a state insulated from the base 3 and partlylocated outside the groove 5. The dummy lead pin 11D, like the lead pin11A, is fixed to the base 3 in a state electrically conductivetherewith, with one end of the lead pin 11D joined to the base 3 bywelding or the like. The lead pin 11D, like the lead pin 11A, isarranged in a position where it overlaps the heat sink 4 as seen in aplan view projected from the direction of the axis X. The lead pin 11Dis arranged in the same position where, in a common three-pin device, alead pin for outputting a monitoring signal is arranged. This makes thepin arrangement here compatible with that of common three-pin devices,and thus makes it possible to share the same fabrication equipment tofabricate them.

In a device incorporating a monitoring function, the lead pin foroutputting the monitoring signal needs to be arranged, like the lead pin11B, so as not to overlap the heat sink 4 as seen in a plan view. Thislimits the position where the heat sink 4 can be located. In thisembodiment, however, since the lead pin 11D is a dummy lead that doesnot protrude from the base 3, it is possible to secure a wide area werethe heat sink 4 can be located. That is, in the area where a lead pinfor outputting a monitoring signal would otherwise be located, it ispossible to locate the heat sink 4, specifically, in this example, topermit the wall 7B to protrude therefrom.

As a result, it is possible to locate the upper end of the heat sink 4,which is usually located at the same level as the surface 6, at a levelhigher than the light emission point or upper surface of thesemiconductor laser element 9. The presence of this wall 7B protrudingto a level higher than the light emission point or upper surface helpsincrease the volume or surface area for heat dissipation and therebyachieve satisfactory heat dissipation.

The ninth embodiment can be applied t any of the second to eighthembodiments and to other embodiments.

Next, a tenth embodiment of the invention will be described withreference to FIG. 10. Such components as are found also in theembodiment shown in FIG. 9 are identified with the same referencenumerals, and their explanations will be omitted; that is, the followingdescription centers on differences from the ninth embodiment. Thedifference from the ninth embodiment is that the wall 7 of the heat sink4 is differently shaped. Specifically, the wall 7 has the summitthereof, which has an acute angle in the ninth embodiment, chamfered soas to be formed into a flat surface 7C. This construction, thoughslightly less effective in heat dissipation than the ninth embodiment,offers the same effects as the ninth embodiment.

Next, an eleventh embodiment of the invention will be described withreference to FIG. 11. This embodiment is a combination of the embodimentshown in FIG. 8 having the embodiments shown in FIGS. 9 and 10 addedthereto. Accordingly, such components as are also found in FIGS. 8 to 10are identified with the same reference numerals.

The base 3 and the heat sink 4 are given the same diameter so as not toproduce a level difference between them. Part of a cylindrical member iscut out to form the heat sink 4, and the remaining part that has notbeen cut out is used as the base 3. By giving the base 3 and the heatsink 4 such an integral cylindrical shape and thereby eliminating thelevel difference between them, it is possible to eliminate therestrictions imposed by such a level difference when the fittingposition of the semiconductor laser device is adjusted by moving italong the direction of the axis X. This makes adjustment easy.

One end of the lead pin 11B, which is fixed to the base 3 by theinsulating member 13, penetrates the base 3 and extends to above theflat surface 6B. The lead pin 11D, like the lead pin 11A, is fixed tothe base 3 in a state electrically conductive therewith, with one end ofthe lead pin 11D joined to the base 3 by welding or the like. The leadpin 11D, like the lead pin 11A, is arranged in a position where itoverlaps the heat sink 4 as seen in a plan view projected from thedirection of the axis X. The lead pin 11D is arranged in the sameposition where, in a common three-pin device, a lead pin for outputtinga monitoring signal is arranged. This makes the pin arrangement herecompatible with that of common three-pin devices, and thus makes itpossible to share the same fabrication equipment to fabricate them. Thewall 7A has the summit thereof chamfered so as to be formed into a flatsurface 7C.

The eleventh embodiment offers the same effects as the eighth to tenthembodiments.

In the embodiments described above, it is also possible to use, as asemiconductor light-emitting element of a different type from thesemiconductor laser element 9, a light-emitting diode. It should beunderstood that many variations and modifications other than thosespecifically described above in connection with the embodiments arepossible within the scope and spirit of the present invention.

Industrial Applicability

A semiconductor laser device according to the present invention can beused as a light source for an optical disk such as a CD, CD-R/RW, DVD,DVD-R/RW, DVD-BlueRay disk, and the like, and in particular as asemiconductor laser device having a compact package suitable for use asa slim (thin) pickup for an optical disk.

1. A semiconductor laser device characterized in that a groove is formedin a cylindrical heat sink along an axial direction thereof and in thata semiconductor laser element is placed on an inner wall surface of thegroove.
 2. A semiconductor laser device having a package comprising acircular base and a heat sink and having a semiconductor laser elementplaced on the heat sink, characterized in that the heat sink iscylindrical and concentric with the base, in that a groove is formed inthe heat sink along an axial direction thereof, and in that thesemiconductor laser element is placed on an inner wall surface of thegroove.
 3. A semiconductor laser device according to one of claims 1 and2, wherein the groove is formed so deep as to include a center axis ofthe cylindrical heat sink.
 4. A semiconductor laser device according toone of claims 1 and 2, wherein the groove is so shaped as to completelyhouse therein the semiconductor laser element.
 5. A semiconductor laserdevice according to one of claims 1 and 2, wherein the groove is soshaped as to completely house therein the semiconductor laser elementalong with bonding wires connected thereto.
 6. A semiconductor laserdevice according to one of claims 1 and 2, wherein walls located at bothsides of the groove extend to a height higher than the semiconductorlaser element.
 7. A semiconductor laser device according to one ofclaims 1 and 2, wherein the groove is formed by cutting off an arcsurface of the heat sink equivalent to a center angle of 180 degrees orless.
 8. A semiconductor laser device according to claim 2, wherein alead pin is provided that, at one end thereof, penetrates the base, andthe lead pin is, at the other end thereof, located in the groove.
 9. Asemiconductor laser device according to claim 2, wherein two lead pinsare provided that, at one ends thereof, penetrate the base, and the leadpins are, at one ends thereof, located in the groove.
 10. Asemiconductor laser device according to one of claims 1 and 2, whereinthe heat sink has a tapered surface formed along an outer edge of a tipend thereof.
 11. A semiconductor laser device according to one of claims1 and 2, wherein the heat sink has a tip end thereof formed into aspherical surface.
 12. A semiconductor laser device according to one ofclaims 1 and 2, wherein the heat sink has a bottom surface thereofformed flat.
 13. A semiconductor laser device according to one of claims1 and 2, wherein a flat-plate-shaped optical element is attached to afront end surface of the heat sink.
 14. A semiconductor laser deviceaccording to one of claims 1 and 2, wherein a spherical optical elementis attached to a front end surface of the heat sink.
 15. A semiconductorlaser device according to claim 2, wherein the base and the heat sinkare formed of a same metal.
 16. A semiconductor laser devicecharacterized in that a groove so deep as to completely house therein asemiconductor laser element is formed in a columnar heat sink, and inthat the semiconductor laser element is placed on a bottom of thegroove.
 17. A semiconductor laser device comprising a semiconductorlaser element and a columnar heat sink having a flat surface that isparallel to an optical axis of the semiconductor laser element and onwhich the semiconductor laser element is placed, characterized in thatthe heat sink has a wall formed integrally therewith at one of left-handand right-hand sides of the flat surface with respect to the opticalaxis, and in that a summit of the wall is located higher than thesemiconductor laser element and than a bonding wire connected thereto.